Liquid spraying guns

ABSTRACT

A spray gun for spraying articles such as automobile bodies fed in succession is automatically controlled by a selectively operable valve having a plurality of liquid delivery ports and gun purging ports. The liquid delivery ports are connected one each to sources of liquid of different colors and the gun purging ports to a source of compressed gas and a source of solvent. A single hollow arm connected by a feed hose to the gun is movable relative to the ports of the valve under control of a program unit and a timer in a manner such that when the program unit signals the requirement for a change of color the timer causes the hollow arm to be moved from the current liquid delivery port first to the compressed gas gun purging port so that a slug of air is delivered into the hollow arm and then to the solvent gun purging port so that solvent is delivered to complete the emission of colored liquid from the arm, the feed hose, and the gun and to effect cleansing of these parts preparatory to the delivery of liquid of a different color. The compressed gas and solvent is fed at a pressure sufficient to maintain the feeding pressure of liquid remaining in the arm, the feed hose, and the gun until the liquid is emitted from the gun.

United States Patent 1 Knight Feb. 13, 1973 LIQUID SPRAYING GUNS Primary Examiner-Lloyd L. King [75] Inventor: Howard Richard James Knight, Assistant Exammer Mlchael Mar Hampton, England Attorney-Snyder and Butrum [73] Assignee: Carrier Engineering Company [57] ABSTRACT Limited, London, England A spray gun for spraying articles such as automobile [22] Filed: Aug. 28, 1970 bodies fed in succession is automatically controlled by a selectively operable valve having a plurality of li uid [21] Appl' N 67869 delivery ports and gun purging ports. The liiiuid delivery ports are connected one each to sources of [30] Foreign Application Priority Data liquid of different colors and the gun purging ports to a source of compressed gas and a source of solvent. A Sept. 3, 1969 Great Britain ..43,668/69 Single hollow arm connected by a feed hose to the g is movable relative to the ports of the valve under con- [52] US. Cl. ..239/1l2, 137/240, l37/624.l 8, no] of a program unit and a timer in a manner such 137/62420 137/625' that when the program unit signals the requirement [51] hit. Cl. for a change of color the timer causes the hollow arm [58] iflqfi f h 239/104 H2; .137/6241 to be moved from the current liquid delivery port first 137/6242), 62511 x to the compressed gas gun purging port so that a slug of air is delivered into the hollow arm and then to the [56] References Cited solvent gun purging port so that solvent is delivered to complete the emission of colored liquid from the arm, UNITED STATES PATENTS the feed hose, and the gun and to effect cleansing of 3,348,774 10/1967 Wiggins. ..239/ll2 X these parts preparatory to the delivery of liquid of a 3,373,762 1968 K0r ha 3 X different color. The compressed gas and solvent is fed 3,403,695 10/1968 HOpklllS ..239/l12 X at a pressure ufficient to maintain the feeding pres- 3,145,930 8/1964 Hefklotz a 3L min/62511 X sure of liquid remaining in the arm, the feed hose, and 3,240,225 3/1966 Barrows ..l37/6l4.ll X

the gun until the liquid is emitted from the gun.

9 Claims, 7 Drawing Figures PATENTED FEB I 3 1975 SHEET10F4 PATENTEDFEB13 1913 3.716.191

SHEET 20F 4 I I 03 Q3 12% && N)

I murder PAIENTEDFEBIBIBIS 3.716191 SHEET3DF4 1 Inventor LIQUID SPRAYING GUNS BACKGROUND OF THE INVENTION This invention relates to an apparatus for controlling the operation of a spray gun and it has particular application in the automatic spraying of a succession of articles, for example automobile bodies, each with a liquid of a different color.

It is sometimes necessary to spray a succession of such articles each with a different one of as many as say eighteen different colors using the same spraying apparatus and it is necessary to ensure that there be no recognizable contamination of the colors in the apparatus and that the changeover from one color to another be performed in a minimum of time. In the spraying of automobile bodies the interval of time between the end of spraying one body and the beginning of spraying the next may be very short.

The present invention has considerable advantages in spray painting systems of the type described, for example, in U.S. Pat. specification No. 3,128,787 where a spray gun is supplied with paint of different colors via a single coupling pipe from a selector and valve device.

SUMMARY According to the invention there is provided apparatus for controlling the operation of a spray gun, said'apparatus comprising valve means including a plurality of liquid delivery ports each connectable with a different source of liquid tobe sprayed by the gun on to an article and gun purging ports each connectable with a source of purging fluid, feed means co-operable with and movable relative to said ports and connectable with the spray gun by a feed hose, selector means coupled to the feed means and operable selectively to position the feed means for co-operation with any one of the ports, purging fluid delivery control means connected with each of the gun purging ports, a program unit coupled to the selector means and operable to effect operation thereof, and timing means coupled to the program unit and said purging fluid delivery control means and operable to determine the sequence and duration of cooperation of the feed means with one of said predetermined ones of the ports and the gun purging ports and to control operation of the purging fluid delivery control means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of a selector and valve device and associated pneumatic and electrical circuits,

FIG. 2 is a perspective view of the selector valvev DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown diagrammatically at 1 valve means having twenty inlet ports, a number of which are indicated at 2, arranged around a circle 3. Each one of eighteen of these ports, of which those numbered 4, 5, 6 and 21 are illustrated, is connected via individual hoses 71, FIGS. 2 and 5, to a source, not shown, of paint of a different color from the others. The remaining two ports indicated at 22 and 23 are respectively first and second purging ports connected via separate hoses 71 to a supply of solvent and a compressed gas supply respectively which constitute purging fluids. The gas, in the particular embodiment, is air.

A radially extending tubular selector arm 25, FIG. 1, is attached to a pinion 26 which cooperates with a rack 27 in such a way that longitudinal movement of the rack causes the arm 25 to rotate and one end 28 of the arm 25 to move over the twenty ports. The end 28 of the tubular'arm 25 is so designed that it cooperates with a sealing ring, described below, associated with the inlet ports to provide a fluid-tight seal between a respective port and the tubular arm 25. A flat annular valve plate, indicated by the dotted lines 29 extends on either side of the arm 25 and rotates with the arm 25, cooperating with the sealing ring to seal each of the ports not coupled to the arm 25 The valve plate 29 is provided with a single opening therethrough which is aligned with the end 28 of the tubular arm 25 so that in any selected position of the valve plate all but one of the ports is obturated. The other end 30 of the tubular arm 25 is coupled to a feed-hose indicated by a dotted line 31 providing a feed to spray guns 32 and 33. A path may thus be selected and opened between any one of the supplies of paint, or the supply of air, or of solvent, and the spray guns.

The rack 27 has one end 35 connected to the piston of a double .acting cylinder 36 and its other end 37 movable backwards and forwards within a pneumatically operated stop block 38. The stop block 38, as will be explained below in more detail, has a central bore in which the end 37 of the rack may move and nineteen double acting pneumatically operated piston stops 39 having cylindrical extensions which may be moved selectively transversely into and out of the bore in order to provide stop members for the end 37 of the rack 27 at selected positions. Eighteen of the stops 39 are operated by means of compressed air supplied via pipes indicated at 41 and respective ones of a plurality of solenoid valves CS from a source 42. The eighteen solenoid valves CS are each connected electrically to a program unit 43 in such a way that any one of the solenoids may be operated according to a predetermined program. The nineteenth stop 39 is connected via a compressed air supply line ASL and a double acting solenoid valve S to a supply line 40 of compressed air. The solenoid of the solenoid valve S is connected to one output from a timing unit T providing electrical signals via a lead 45. Another output from the program unit 43 is applied to the timer T via a lead 44. Operation of the solenoid valve S also causes the operation of a spool valve 47 connected in the supply hose SSH to the port 22 and controlling the flow of solvent from the supply line SSL to the port 22 of the selector and valve device in order to ensure that there is no leak of the highly penetrating solvent at the valve seal.

With the piston of the cylinder 36 fully within the cylinder, the rack 27 is not positioned against any of the nineteen stops in the stop block 38, but it is located in a twentieth position longitudinally. The cylinder 36 is supplied with compressed air from the supply line 40 over the lines 48 and 49 via a solenoid valve CV. The operation of the valve CV is controlled by an output on the lead 51 from the timing unit T.

Atomizing air is supplied to the spray guns 32 and 33 via lines 53 and 54 from the supply line 40 under the control of a spool valve 55 connected to and controlled by a double acting solenoid valve A which is also supplied with air from the supply line 40. The operation of the solenoid of the solenoid-valve A is controlled by an output on a lead 57 from the timing unit T.

A solenoid valve C which is operated by an output from the timing unit on a lead 58 is connected to and controls the operation of a spool valve 59. The spool valve 59 is in lines 61 and 62 supplying air from the supply line 40 to operate control pistons in the spray guns 32 and 33. These control pistons determine when paint should be allowed to pass into the atomizing chambers of the spray guns. Thus the valve C controlling the spool valve 59 is able to control the flow of paint into the guns 32 and 33 after the automatic painting operation.

In operation information is fed to the program unit 43 according to the colors to be applied to the successive articles, for example automobile bodies, to be painted by means of the guns 32 and 33. This information may be supplied to the program unit by a slide register, not shown, comprising a series of contacts, which may be manually or computer operated according to the color required. This infonnation is thereby effectively stored, and at instants of time determined by the program, the timer unit T and the appropriate solenoid valve CS are instructed to operate. Information concerning the body style is fed to the program unit so that the program unit may decide exactly the correct time instant to begin the cycle of changeover operations according to the relative positions of the body and the spray guns. The control of the whole operation is by means of the program unit and the timing unit T which may, for example, be an electrically operated rotary timer having a cam shaft arranged to operate signal contacts in a given sequence and with given time intervals as instructed by the program unit. Other well-known forms of timing unit, for example relay operated circuits, may be used.

In a particular embodiment the feed-hose 31 connecting the spray gun 33 to the end 30 of the tubular arm 25 may be of such a length that in order to reduce the waste of paint to a minimum and to shorten the changeover time between one color and the next it is possible to commence the purging operation by introducing a purging fluid into the end of the feed-hose 31 connected to the arm 25 before all of the paint in the feed-hose 31 and the spray guns has been used.

The description of the operation of the system will now be made starting from an instant of time when the spraying of an article has reached the stage at which there is sufficient paint remaining in the feed-hose 31 and the guns to complete the spraying of the article. At

this instant a signal is given from the program unit to start the cycle of operation.

First the solenoid valve CV is operated to cause the piston of the air cylinder 36 to move fully into the cylinder and the rack 27 to move into its datum or twentieth position thereby causing the selector arm 25 to rotate until its end 28 is coupled to the air supply port 23 as shown in FIG. 1. The supply of paint to the port with which the selector arm has been coupled is thus automatically cut off by the rotation of the valve plate 29. With the selector arm 25 coupled to the air supply port 23 the timing unit operates a spool valve 147 in line PA so that at compressed air a pressure sufficient to maintain the pressure of the paint in the hose is applied via the arm 25 to the paint in the hose 31.

The article is, at this instant of time, still being painted and as soon as the required amount of air, known as a slug of air, has been supplied to the hose 31, the timer contacts operate the solenoid valve S causing the stop 39 for the nineteenth position of the rack 27 to be energized. The operation of the valve S also causes the spool valve 47 to be operated and to open the supply of solvent to port 22 of the device 1. The solenoid valve CV is then operated by the timing unit in such a way as to cause the rack 27 to move into the nineteent position against the stop 39 already selected and thereby to rotate the arm 25 and couple the solvent port 22 to the hose 31. Solvent for maintaining paint emission from and purging of the guns then passes into the hose 31 behind the slug of air.

When the painting of the body is completed and the body has moved away the guns automatically stop spraying and come to rest pointing downwards into a spray booth tank. During this time the solvent port 22 is maintained coupled to the hose 31 and the timing unit causes the solenoid valve A to operate in order to cut off the atomizing air from the guns and the solenoid valve C to turn on the control air via lines 61, 62 to open the guns. The opening of the guns permits the solvent to push the remaining paint out of the hose 31 and the guns. Purging with solvent is then continued to finally clean hose 31. The timing unit then causes the solenoid valve CV to be operated to cause the rack 27 to move into the twentieth" position and rotate the selector arm 25 so that the air port 23 is coupled to the hose 31. A blow of air is then given to the guns to push out the solvent. During this period the timing unit causes the solenoid valve S to be restored to retract the stop 39 in the nineteenth" position and close the spool valve 47 to cut off the supply of solvent to the'port 22. At the same time a signal is sent from the program unit 43 to select and operate a particular one of the solenoid valves CS, according to the color required for the next article to be painted, and the appropriate stop 39 to be operated.

The timing unit T then causes the solenoid valve CV to be operated in such a way that the rack 27 is moved until its end 37 abuts against the selected stop 39.

The selector arm 25 is thereby caused to rotate until it couples the newly selected one of the eighteen ports connected to the paint to be sprayed to the hose 31 and paint of the appropriate color is allowed momentarily to pass into the hose 31 and through the guns into the spray booth tank to ensure clean color in the guns. The new article to be sprayed is then positioned in relation to the guns 32 and 33.

Finally the timing unit operates the solenoid valves A and C to restore the atomizing and control air, the spray guns are directed towards'the new article, spraying commences and the timing unit is restored to its initial position.

Referring to FIG. 2 there is shown in a perspective view the selector and valve device 1 having a casing 70 and a plurality of hoses 71 connecting the twenty ports to the sources of paint, solvent, and compressed air. The feedhose 31 is shown providing the feed from the end 30 of the selector arm 25 (not shown) to spray gun (not shown). The rack 27 is arranged within a casing 72 which also covers the pinion 26, and at its end 35 the rack is connected to the piston of the cylinder 36, while at its end 37 the rack enters the stop block 38 having the stops 39.

Referring to FIGS. 3 and 4 the arrangement of the stops 39 within the block 38 is clearly seen. The stops, which are double acting pneumatic stops, are staggered around three of the four faces of the block 38 which has a central longitudinal bore 74 for the end 37 of the rack 27. The operating air for the stops is passed to them via hose connections 41 and air from a common source is supplied under pressure via passageways 75 and 76 for the return of the pistons. The pistons are caused to operate upon the introduction of air via the connections 41 by virtue of the differential resulting from the differences in surface areas presented to the operating and return air respectively by the pistons. The pistons 77 of the stops 39 each have stop members 78 which extend into the bore 74 when the pistons are operated, as indicated at 79, thereby providing a respective stop for the end 37 of the rack 27.

Referring to FIG. 5 there is shown diagrammatically the path of the feed hose coupling the selector and valve device 1 to a spray gun for spraying an automobile body. The hose 31 extends from the center of the device 1 to the fixed end 80 of a travelling belt 81 of the kind described in British Pat. specification No. 942955. The hose is'supported by the travelling belt 81 until it reaches the end 82 of the belt. The hose 31 then extends in a gun arm as indicated by the dotted line 84 to the spray gun indicated by the arrow 85. It may be seen that, knowing the coverage of the paint, it is a comparatively easy matter to determine at which instant of time or stage of spraying to cut off the supply of paint to the feed-hose 31 and to introduce at the desired pressure a purging fluid, which as in the embodiment described may be a composite fluid of air followed by a solvent followed by air, into .the feed-hose 31, while still enabling the painting of the body to be completed with the paint in the hose and the gun.

Referring to FIGS. 6 and 7 there is shown a part of the valve sealing ring 85 of the selector and valve device 1. The sealing ring is formed from a single annulus of synthetic plastics material with holes 86 extending therethrough and coinciding with the twenty ports of the valve device. Between each port there is a radially extending groove 87 which renders the ring 85 more flexible. The selector arm 25 shown in FIG. 1 cooperates with the rotatable valve plate 29 which rotates with the arm 25 and provides a seal for each of the twenty ports not being used against the ring 85.

In one embodiment a support roller, not shown, for the rack 27 is arranged immediately beneath the pinion 26.

It will be noted that in the embodiment described the pneumatically operated stops 39 are operated only when the rack 27 is in the position when a blow of air is given via the selector and valve device, i.e. when the piston is fully within the cylinder 36, so that there is no side load on the stops 39.

In the particular embodiment described the purging operation comprises the steps of applying a composite purging fluid consisting of a blow of air, a solvent wash and a further blow of air. Of course other combinations of purging fluid are possible and in certain circumstances the purging step may satisfactorily be accomplished by the use of a single fluid.

Although in the particular embodiment described the selector and valve mechanism is of the rotatable type, other types, for example employing a linear movement, may be used.

An advantage of the rotatable selector and valve mechanism described in the particular embodiment is that the connection from the gun to the source of paint is in each case independent of connection to any other of the sources so that in the event of a leak through a valve associated with a color not being used the color being used is not contaminated.

Although a common supply of air is shown in the drawings in practice different supplies may be used or the pressures may be adjusted by means of reducing valves as required.

I claim:

1. Apparatus for controlling the operation of a spray gun, said apparatus comprising valve means including a plurality of liquid delivery ports each connectable with a different source of liquid to be sprayed by the gun on to an article and first and second gun purging ports each connectable with a source of purging fluid, feed means cooperable with and movable relative to said ports and connectable with the spray gun by a feed hose, selector means coupled to the feed means and operable selectively to position the feed means for cooperation with any one of the ports, purging fluid delivery control means connected with each of the first and second purging ports and operable to deliver air under pressure as a purging fluid to the first gun purging port and a liquidpurging fluid to the second gun purging port, a program unit coupled to the selector means and operable to effect operation thereof, and timing means coupled to the program unit and said purging fluid delivery control means and operable to determine the sequence and duration of cooperation of the feed means with one of said liquid delivery ports and the gun purging ports and to control operation of the purging fluid delivery control means.

2. Apparatus according to claim 1, wherein the purging fluid delivery control means includes valves respectively to control the delivery of purging fluid to the first and second gun purging ports and operable under control of the timing unit to permit the flow of purging fluid to the purging ports at a pressure sufficient to maintain the feeding pressure of liquid remaining in the feed means, the feed hose, and the gun on movement of the feed means from cooperation with a liquid delivery port. I

3. Apparatus according to claim 1, wherein the selector means comprises a reciprocable rack coupled to the feed means and slidable lengthwise in a stop block including a plurality of stop valves each provided with a stop member, said valves being operable independently under control of the program unit selectively to interpose the stop members into the path of the rack and to withdraw the stop members from said path.

4. Apparatus according to claim 3, wherein the valve means comprises a stationary member in which the liquid ports and the gun purging ports are spaced apart around a circle, and a valve plate rotatable relative to said stationary member and having a single opening therethrough for selective cooperation with one only of said ports, and wherein the feed means comprises a tubular arm rotatable relative to the stationary member about an axis coincident with the center of said circle, one end of the arm communicating with the opening in the valve plate and the opposite end of the arm communicating with the feed hose and being connected through a pinion with said rack to permit rotation of the arm by the rack.

5. Apparatus according to claim 4, including an annular sealing ring associated with the stationary member, said sealing ring being made of synthetic plastics material and interposed between the valve plate and said member and being provided with holes extending therethrough and coincident with said ports and with radially extending grooves located between the holes to increase the flexibility of the sealing ring.

6. Apparatus according to claim 2, wherein the selector means comprises a reciprocable rack coupled to the feed means and slidable lengthwise in a stop block including a plurality of stop valves each provided with a stop member, said valves being operable independently under control of the program unit selectively to interpose the stop members into the path of the rack and to withdraw the stop members from said path.

7. Apparatus according to claim 6, wherein the rack is operable by the piston of a fluid-operated double-acting cylinder through said solenoid valve.

8. Apparatus according to claim 7, wherein the valve means comprises a stationary member in which the liquid ports and the gun purging ports are spaced apart around a circle, and a valve plate rotatable relative to said stationary member and having a single opening therethrough for selective cooperation with one only of said ports, and wherein the feed means comprises a tubular arm rotatable relative to the stationary member about an axis coincident with the center of said circle, one end of the arm communicating with the opening in the valve plate and the opposite end of the arm communicating with the feed hose and being connected through a pinion with said rack to permit rotation of the arm by the rack.

9. Apparatus according to claim 8, including an annular sealing ring associated with the stationary member, said sealing ring being made of synthetic plastics material and interposed between the valve plate and said member and being provided with holes extending therethrough and coincident with said ports and with radially extending grooves located between the holes to increase the flexibility of the sealing ring. 

1. Apparatus for controlling the operation of a spray gun, said apparatus comprising valve means including a plurality of liquid delivery ports each connectable with a different source of liquid to be sprayed by the gun on to an article and first and second gun purging ports each connectable with a source of purging fluid, feed means cooperable with and movable relative to said ports and connectable with the spray gun by a feed hose, selector means coupled to the feed means and operable selectively to position the feed means for cooperation with any one of the ports, purging fluid delivery control means connected with each of the first and second purging ports and operable to deliver air under pressure as a purging fluid to the first gun purging port and a liquid purging fluid to the second gun purging port, a program unit coupled to the selector means and operable to effect operation thereof, and timing means coupled to the program unit and said purging fluid delivery control means and operable to determine the sequence and duration of cooperation of the feed means with one of said liquid delivery ports and the gun purging ports and to control operation of the purging fluid delivery control means.
 1. Apparatus for controlling the operation of a spray gun, said apparatus comprising valve means including a plurality of liquid delivery ports each connectable with a different source of liquid to be sprayed by the gun on to an article and first and second gun purging ports each connectable with a source of purging fluid, feed means cooperable with and movable relative to said ports and connectable with the spray gun by a feed hose, selector means coupled to the feed means and operable selectively to position the feed means for cooperation with any one of the ports, purging fluid delivery control means connected with each of the first and second purging ports and operable to deliver air under pressure as a purging fluid to the first gun purging port and a liquid purging fluid to the second gun purging port, a program unit coupled to the selector means and operable to effect operation thereof, and timing means coupled to the program unit and said purging fluid delivery control means and operable to determine the sequence and duration of cooperation of the feed means with one of said liquid delivery ports and the gun purging ports and to control operation of the purging fluid delivery control means.
 2. Apparatus according to claim 1, wherein the purging fluid delivery control means includes valves respectively to control the delivery of purging fluid to the first and second gun purging ports and operable under control of the timing unit to permit the flow of purging fluid to the purging ports at a pressure sufficient to maintain the feeding pressure of liquid remaining in the feed means, the feed hose, and the gun on movement of the feed means from cooperation with a liquid delivery port.
 3. Apparatus according to claim 1, wherein the selector means comprises a reciprocable rack coupled to the feed means and slidable lengthwise in a stop block including a plurality of stop valves each provided with a stop member, said valves being operable independently under control of the program unit selectively to interpose the stop members into the path of the rack and to withdraw the stop members from said path.
 4. Apparatus according to claim 3, wherein the valve means comprises a stationary member in which the liquid ports and the gun purging ports are spaced apart around a circle, and a valve plate rotatable relative to said stationary member and having a single opening therethrough for selective cooperation with one only of said ports, and wherein the feed means comprises a tubular arm rotatable relative to the stationary member about an axis coincident with the center of said circle, one end of the arm communicating with the opening in the valve plate and the opposite end of the arm communicating with the feed hose and being connected through a pinion with said rack to permit rotation of the arm by the rack.
 5. Apparatus according to claim 4, including an annular sealing ring associated with the stationary member, said sealing ring being made of synthetic plastics material and interposed between the valve plate and said member and being provided with holes extending therethrough and coincident with said ports and with radially extending grooves located between the holes to increase the flexibility of the sealing ring.
 6. Apparatus according to claim 2, wherein the selector means comprises a reciprocable rack coupled to the feed means and slidable lengthwise in a stop block including a plurality of stop valves each provided with a stop member, said valves being operable independently under control of the program unit selectively to interpose the stop members into the path of the rack and to withdraw the stop members from said path.
 7. Apparatus according to claim 6, wherein the rack is operable by the piston of a fluid-operated double-acting cylinder through said solenoid valve.
 8. Apparatus according to claim 7, wherein the valve means comprises a stationary member in which the liquid ports and the gun purging ports are spaced apart around a circle, and a valve plate rotatable relative to said stationary member and having a single opening therethrough for selective cooperation with one only of said ports, and wherein the feed means comprises a tubular arm rotatable relative to the stationary member about an axis coincident with the center of said circle, one end of the arm communicating with the opening in the valve plate and the opposite end of the arm communicating with the feed hose and being connected through a pinion with said rack to permit rotation of the arm by the rack. 